Factor analysis and the index of clustering

The initial problem of factor analysis is described as a search for clustering of the test vectors. Curves are developed which give a visual picture of the clustering tendency, and an index of clustering is derived which provides a simple estimate for the number of factors.Based, in part, on a paper Matrix Approximation Criteria read at the District meeting of the Psychometric Society, Chicago, April 3, 1937. The author wishes to acknowledge suggestions gained in conversations with Dr. A. S. Householder and Mr. Clyde Coombs, of the University of Chicago.